原理从简单到复杂递进,代码从少到多实现
简介:
UDP无连接,不稳定
客户端和服务端:没有明确的界限不管有没有准备好,都可以发给你导弹
DDos:洪水攻击(饱和攻击)
利用此原理可以实现发短信功能,不需要双方在线接收消息,一个只要将消息发送出去,另外一个可以随缘就接收,这点与TCP实现通信相反,在我看来TCP实现通信类似于打电话,必须双方同时在线.
源码展示:
客户端:
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
//UDP不需要连接服务器
public class UdpClientDemo01 {
public static void main(String[] args) throws Exception{ //1.建立一个Socket
DatagramSocket socket=new DatagramSocket();
//2.建一个包
String msg="你好呀,服务器!";
//发送给谁
InetAddress localhost = InetAddress.getByName("localhost");
int port =9090; DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, 9090);
//3.发送包
socket.send(packet); //关闭流
socket.close();
服务器端:
package com.lesson03;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
//UDP不需要连接服务器
public class UdpClientDemo01 {
public static void main(String[] args) throws Exception{
//1.建立一个Socket
DatagramSocket socket=new DatagramSocket();
//2.建一个包
String msg="你好呀,服务器!";
//发送给谁
InetAddress localhost = InetAddress.getByName("localhost");
int port =9090;
DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, 9090);
//3.发送包
socket.send(packet);
//关闭流
socket.close();
}
}
由客户端,服务器端,可以转变为两个用户之间的通信
开启线程,实现双方相互通信:首先实现两个方法:接收方,和发送方!注意两个类都实现了Runable接口talkSend:
talkSend:package com.qiu.chat;import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;public class TalkSend implements Runnable {
DatagramSocket socket=null;
BufferedReader reader =null;
private int fromPort;
private String toIp;
private int toPort; public TalkSend(int fromPort, String toIp, int toPort) {
this.fromPort = fromPort;
this.toIp = toIp;
this.toPort = toPort; try {
socket = new DatagramSocket(fromPort);
//准备数据,控制台读取system.in
reader = new BufferedReader(new InputStreamReader(System.in));
} catch (Exception e) {
e.printStackTrace();
}
}
@Override
public void run() { //准备数据,控制台读取system.in while (true) {
try { String data = reader.readLine();
byte[] datas = data.getBytes(); DatagramPacket packet = new DatagramPacket(datas,0,datas.length,new InetSocketAddress(this.toIp,this.toPort));
socket.send(packet);
if (data.equals("bye")) {
break;
}
}catch (Exception e) {
e.printStackTrace(); }
}
socket.close();
}
}
talkReceive:
package com.qiu.chat;import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;public class TalkReceive implements Runnable { DatagramSocket socket =null;
private int port;
private String msgFrom; public TalkReceive(int port,String msgFrom) {
this.port = port;
this.msgFrom=msgFrom;
try {
socket = new DatagramSocket(port);
} catch (SocketException e) {
e.printStackTrace();
}
} @Override
public void run() { while (true) {
try {
//准备接收的包裹
byte[] container = new byte[1024];
DatagramPacket packet = new DatagramPacket(container,0,container.length);
socket.receive(packet);//阻塞式接收包裹
//断开连接的判断
byte[] data = packet.getData();
String receiveData = new String(data, 0, data.length);
System.out.println(msgFrom+":"+receiveData);
if(receiveData.equals("bye")){
break;
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
定义两个对象,来开启线程.核心代码就是new Thread().start,注意端口号是否一致!
Boss:
package com.qiu.chat;public class TalkStudent {
public static void main(String[] args) {
//开启两个线程
new Thread(new TalkSend(7195,"LocalHost",10086)).start();
new Thread(new TalkReceive(10010,"Boss")).start();
}
}
employee:
package com.qiu.chat;public class TalkTeacher {
public static void main(String[] args) {
new Thread(new TalkSend(10000,"LocalHost",10010)).start();
new Thread(new TalkReceive(10086,"employee")).start();
}
}
代码实现之后,即可实现boss与employee之间的通信.